In coronary artery disease, stenotic plaques form within the coronary arteries, restricting and in some cases completely blocking blood flow to the heart muscle. In recent years, a number of different catheter-based interventions have been developed to treat coronary artery disease, including percutaneous transluminal coronary angioplasty (PTCA) and stenting. PTCA involves the placement of an endovascular catheter into the diseased coronary artery and expanding a balloon within the stenotic lesion to dilate the lumen, thereby improving blood flow through the treated area. One drawback of PTCA has been the tendency in some cases for the coronary artery lumen to “restenose” following dilatation, wherein plaque reforms at the treatment site to narrow or block the lumen. Coronary stenting has been developed in part to address this restenosis problem. In coronary stenting, a tubular stent is positioned within the coronary lesion using an endovascular delivery catheter. The stent is expanded within the lesion and implanted in its expanded state, maintaining the patency of the arterial lumen.
Even after stenting, however, some patients experience restenosis. While the causes of restenosis are not fully understood, a number of different technologies have been developed to reduce restenosis following stenting. One such technology that has shown a great deal of promise is the use of drug-coated stents that gradually elute anti-stenosis agents into the wall of the coronary artery. Another approach is the use of radioactive stents that deter cell proliferation at the treatment site. A further approach involves the optimization stent geometry and maximizing stent flexibility to reduce the vascular response that results in cell proliferation following stent placement.
With these new stent technologies showing promising reductions in restenosis rates, stents may begin to be used in new and different ways. Stents may be used in arteries of shape and size heretofore untreatable, both in the coronary vasculature and in other parts of the body. Stents of substantially greater length may be used to treat longer lesions than has been possible before. Stents may be used to “pave” long sections of diseased or disease-prone arteries. Stents may be deployed in arteries that are much smaller than could be stented before, in highly curved vessels, as well as in more tapered vessels.
Current stents and stent deployment devices, however, are not well-suited to address these new potential applications for stents. For example, current stents are designed for treating relatively short lesions, and often are not suitable for longer lesions through which the vessel may be curved, tapered or have other complex geometries. Likewise, current stent deployment catheters function effectively to deliver stents of relatively short length in shorter vascular lesions, but they do not perform well in treating longer, tapered, and/or curved vessels. For example in tapered vessels, current stent deployment catheters may fail to fully expand the stent at its proximal end, while potentially over-expanding the stent at its distal end. Moreover, current stent and stent delivery technology is limited to deploying stents of predetermined length, requiring advance selection of a stent and associated catheter to match the lesion to be treated. Following introduction of the device, should the user wish to treat a longer section of the vessel, the user must remove the delivery catheter from the body and exchange it for a different catheter having a longer stent, or attempt to deploy multiple stents in close proximity to one another, each requiring introduction of new delivery catheter.
What is needed, therefore, is a stent delivery catheter suitable for deployment of long or short stents in long or short vascular lesions and in curved or tapered vessels. The stent delivery catheter should be further adapted for delivering multiple independent, stents or stent segments simultaneously or serially, as well as for selecting and deploying a stent of desired length without removing the delivery catheter from the body.